Here is a photograph of Washington Boulevard at Arlington in the early 1920s. I’d say it’s safe to surmise that the “United” blade sign in the fancy-fronted building at center belonged to the United Arlington Theatre, later to become the Maynard Theatre.

I don’t know if this was the final closure of the Maynard Theatre or not, but Boxoffice magazine’s issue of May 6, 1950, carried a brief item saying that Harry Vinnicof had shuttered the Maynard Theatre due to poor business conditions.

The theater must have been called The Gem after the 1929 article posted above. This is from March 26, 1930 in the LA Times:

ROBBERIES CONFESSED BY YOUTHS
Six Drug Stores, Theater and Oil Station Declared to Have Been Held Up
Robbery of six drug stores, one theater and one oil station was confessed yesterday by Milton Wilkinson, 25 years of age, and Bert Slight, 21, both of 653-A Brooks avenue, Venice, according to Detective Lieutenants Heintelzman and Board.
The men were arrested on the 21st inst. by Officers Schmidt and Dorsey when they recognized the license number of the pair’s automobile as that reported by Joe Shea as having been on the car of two bandits who held him up in his drug store at 5851 West Boulevard on the 14th inst.
Identified by Shea, according to the detectives, the youths readily confessed and implicated themselves voluntarily in the other robberies. The theater hold-up was that of H.H. Hicks in the Gem Theater at 2488 West Washington Boulevard on the 16th inst.